1. Field of the Invention
The present invention relates to a variable valve apparatus of an internal combustion engine, which varies the phase of an intake valve or an exhaust valve.
2. Description of the Related Art
Many reciprocating engines mounted in automobiles include a variable valve apparatus for changing the phases of an intake valve and an exhaust valve, for reasons of engine gas emission countermeasures, fuel consumption reduction and the like.
Many of such variable valve apparatuses employ a structure in which the phase of a cam formed on a camshaft is replaced with an oscillating cam in which a base circular zone and a lift zone are ranging. Specifically, a structure is employed in which an oscillating range of the oscillating cam is changed, whereby a valve opening period and a valve lift amount of the intake valve and the exhaust valve driven via a rocker arm are varied continuously.
In order to improve a pumping loss, a structure is proposed in Jpn. Pat. Appln. KOKAI Publication No. 2003-239712 in which a transmission arm is interposed between a cam and an oscillating cam, and the transmission arm is oscillatably supported by a control shaft.
Specifically, the transmission arm is moved by the turning displacement of the control shaft. A contact position where the transmission arm contacts the cam is changed by moving the transmission arm. By changing the contact position of the transmission arm and the cam, the valve characteristics, that is, a valve opening period, valve open-close timing and a valve lift volume are continuously varied.
In such a variable valve apparatus, it is desired that a variable range from a high valve lift to a low valve lift is expanded.
However, it is difficult to expand the variable range of the valve characteristics. In particular, in the case of a variable valve apparatus in which a transmission arm is moved, a range to move the transmission arm is limited in terms of the supporting structure of the transmission arm, and further regulated by devices and components arranged around the transmission arm. For this reason, it is difficult to expand the variable range easily.